Wind turbines, which are also referred to as wind power plants, are subjected to a variety of influences which excite vibrations. Furthermore, in particular the nacelle of a wind turbine is subjected to permanent vibrations because of the rotation of the rotor hub and the rotor blades connected to the nacelle, even if the wind is incident on the rotor blades at a constant speed.
Monitoring the vibration behavior of wind turbines using acceleration sensors, which are attached to a component of the wind turbine, preferably to the nacelle of the wind turbine, is known from the prior art. Acceleration values representing accelerations of the component may be detected by means of the acceleration sensors, which values are processed by a controller of the wind turbine by comparing the detected acceleration values to predefined acceleration limiting values. If an acceleration limiting value is exceeded, alarms are triggered and/or the wind turbine is stopped. This type of vibration monitoring involves a simple sensor system and a simple monitoring logic, which are provided in every wind turbine due to permitting guidelines and/or certification requirements.
This type of vibration monitoring is used to prevent the wind turbine from temporarily entering resonance. Such resonances can arise due to unfavorable external excitations/influences, thus, for example, unusual wind and/or wave conditions and also malfunctions of the wind turbine regulation. A longer continuous operation of a wind turbine in the state of resonance can result in damage and short-term structural failure of components of the wind turbines.
The acceleration limiting values for triggering an alarm and for initiating a shutdown of the wind turbine are relatively high, and therefore only a few alarm triggers and shutdowns occur in regular operation of the wind turbine. Furthermore, the method for monitoring the vibration state of a wind turbine known from the prior art has the problem that the acceleration limiting value for triggering an alarm is frequently only reached when, for example, the structural integrity of a rotor blade is restricted in such a manner that, a very short time (a few seconds) after exceeding the acceleration limiting value to trigger an alarm, the acceleration limiting value for the shutdown of the wind turbine is already exceeded, because damage to the rotor blade proceeds very rapidly, for example an entire rotor blade is thrown off.
This form of monitoring the vibration state is suitable for avoiding short-term structural failure due to resonance-related overload. This monitoring of threshold value or limiting value is not suitable for a state evaluation of the entire wind turbine or individual component parts/components thereof, for example the rotor blades, since small differences in the vibration behavior do not result in triggering of the alarm or shutdown thresholds, which are very high.